Hi there.. primary infertility ie difficulty in conceiving could be due to husband or wife related causes or both.. sometimes even both are normal yet there might be difficulty in conceiving due to improper timing and method of intercourse.. tell her to have intercourse during 10th to 20th day of her menstrual cycle.. it's during that time she will ovulate( produce egg) and chances of fertilisation is high.. hypothyroidism can also cause difficulty in conceiving but since she just started treatment, you can wait til 3 months.. if they are very anxious to have baby then you could take second opinion..